The invention relates generally to fuel injection systems, and more particularly to an aerodynamic pylon fuel injector system for a combustor, for example a reheat combustor.
A gas turbine system includes at least one compressor, a first combustion chamber located downstream of the at least one compressor and upstream of a first turbine, and a second combustion chamber (may also be referred to as “reheat combustor”) located downstream of the first turbine and upstream of a second turbine. A mixture of compressed air and a fuel is ignited in the first combustion chamber to generate a working gas. The working gas flows through a transition section to a first turbine. The first turbine has a cross-sectional area that increases towards a downstream side. The first turbine includes a plurality of stationary vanes and rotating blades. The rotating blades are coupled to a shaft. As the working gas expands through the first turbine, the working gas causes the blades, and therefore the shaft, to rotate.
The power output of the first turbine is proportional to the temperature of the working gas in the first turbine. That is, the higher the temperature of the working gas, the greater the power output of the turbine assembly. To ensure that the working gas has energy to transfer to the rotating blades within the second turbine, the working gas must be at a high working temperature as the gas enters the second turbine. However, as the working gas flows from the first turbine to the second turbine, temperature of the working gas is reduced. Thus, the power output generated from the second turbine is less than optimal. The amount of power output from the second turbine could be increased if the temperature of the working gas within the second turbine is increased. The working gas is further combusted in the second combustion chamber so as to increase the temperature of the working gas in the second turbine.
In a conventional system, a gas turbine engine uses a second combustor in which a plurality of axially oriented cylindrical injectors are used to inject gaseous fuel and air. The conventional injection systems have a limited number of fuel injection locations or nozzles creating non-uniform distribution of fuel in the combustion chamber. As a result, related problems such as combustion dynamics due to non-uniform mixing of fuel and non-uniform heat release may occur. The conventional injection system also generates significant pressure drop within the combustion chamber.
There is a need for an improved fuel injection system for a combustor, particularly for a reheat combustor.